The use of hyperthermia in treatment of malignant tumors is well known and documented. A summary report reflecting the state of the art in 1982 appears in the following publication:
Manning, M. R., T. C. Cetas, R. C. Miller, J. R. Oleson, W. G. Connort, and E. W. Gerner, "Clinical Hyperthermia, Results of a Phase I Trial Employing Hyperthermia Alone or in Combination with External Beam or Interstitial Radiotherapy," Cancer Vol. 49, pp. 205-216, 1982.
One type of hyperthermia treatment employs capacitive heating of the tumor by means of a pair of electrodes placed on opposite sides thereof. Because significant amounts of electrical energy are involved, the problem of capacitive matching between the power amplifier and the capacitive load arises. As is well known, absence of good capacitive matching in a system causes a relatively large amount of wasted reflected power, thus requiring a much larger power amplifier than would otherwise be necessary, unwanted heating of the electrodes resulting in heat damage to the skin and subcutaneous layers of the patient's body.
In hyperthermia applications, it has been found by the inventors that adjustments in the capacitive matching should be made continually, in response to even minor movements of the patient, even those occasioned by normal breathing. Adjustments in the capacitive matching must also be made in response to the output power supplied to the electrodes. Prior art apparatus does not enable adjustments in capacitive matching to be readily made.